1. Field of the Invention
This invention is concerned with a technique for growing single crystals of mercury tellurate (Hg.sub.3 TeO.sub.6).
2. Description of the Prior Art
Investigations into the properties of high valence tellurium (Te.sup.+.sup.6) oxides have been concerned with compositions of the general formulae M.sub.2 .sup.+.sup.3 TeO.sub.6 and M.sub.3 .sup.+.sup.2 TeO.sub.6, where M is a cation, as indicated. A number of these compositions have found use as phosphors and in piezoelectric applications.
More recently, theoretical predictions have indicated that mercury tellurate (Hg.sub.3 TeO.sub.6) has an acoustic-optic figure of merit that compares favorably with other well-known materials such as lead molybdate (PbMoO.sub.4) and tellurium dioxide (TeO.sub.2). However, in order to fabricate suitable devices for, e.g., acousto-optic applications, single crystals are necessary. The growth Hg.sub.3 TeO.sub.6 crystals has been described by E. B. Hutchins, Jr., in Vol. 27, Journal of the American Chemical Society, pp. 1,157-1,183 (1905). There, crystals of Hg.sub.3 TeO.sub.6 are grown by reacting concentrated aqueous solutions of potassium tellurate and mercury nitrate in an acidic solution. Attempts to reproducibly grow single crystals of sufficient size and optical quality for suitable measurements have not been successful using this technique. In addition, a variety of problems associated with employing well-known crystal growth techniques exist. For example, high temperature growth techniques, such as Czochralski, Kyropolous, Verneuil, etc., require temperatures that are higher than the decomposition temperature of this composition. On the other hand, solution growth techniques require a strong dependence of solubility on temperature, which this composition lacks.